The down side of having a 35mm adapter is that you tend to need more lighting than your normal stock lens. But then all good films are lighted . The good side of it is that you can get D.O.F like a film camera. I've tried two 35mm adapters types.A Static & a spinner type adapter.

The spinner are very heavy and they tend to be loud( because of the motor) So it is not suitable for "gun & go" situations and where you need to record the sound with your camera's on board mic.Best use when it is on a tripod.
But spinners feed on alot of battries. so hence the on going cost.And when the battries run out during a shoot, you will see the difference in your footage.

Static types tend to have a little grain in the picture when you close your lens apeture above f5.6. But in most stuitions i use it at 1.4-2.8 ( i have a nikon 50mm F1.4, nikon 35mm F1.8, nikon 85mm f1.8 )

I've tried making one myself. it cost me about 80euros in parts. but the time and efford taken for research and try and error , i don't want to remember.And the final results of it is o.k, but not compareble to the commercial ones.

This are just my 2cents worth

David